Apparatus for precision bore grinding



Feb. 5, 1952 R. s. PYNE APPARATUS FOR PRECISION BORE GRINDING 6Sheets-Sheet 1 Filed Aug. 2, 1948 Roger .5. Pyne INVENTOR ATT EY Feb. 5,1952 R. s. PYNE 2,584,499

APPARATUS FOR PRECISION BORE GRINDIFNG Filed Aug. 2, 1948 6 Sheets-Sheet2 6 ml /l/ 6 P Q v 25 l6 8 w pum I -.Rager $.Pyne C 42 INVENTOR 173T M I33 BY l ATT EY Feb. 5, 1952 R. s. PYNE 2,584,499

APPARATUS FOR PRECISION BORE GRINDING Filed Aug. 2, 1948 6 Sheets-Sheet3 I I 3/ 34 32 A I 6 I o 0E O G) F) 9 7 Roger .S. Pyne 22 INVENTOR ATTEY R. S. PYNE APPARATUS FOR PRECISION BORE GRINDING Feb. 5, 1952 FiledAug. 2, 1948 Roger 8. Pyne INVENTOR ATTORY m 5a mi. 2 & M RAuwwwwwwvvvvs ==EE=== g all a Feb. 5, 1952 I R. s. PYNE 2,584,499

APPARATUS FOR PRECISION BORE GRINDING Filed Aug. 2, 1948 6 Sheets-Sheet5 III] Roger $.P ne

INVENT R V BYW ATTO EY Feb. 5, 1952 R. s. PYNE APPARATUS FOR PRECISIONBORE GRINDING 6 Sheets-Sheet 6 Filed Aug. 2, 1948 I 1 Y e R 5 k8 Eu W mn T M m u mn m m k m R Y LK B I1 Eu mw km T Ext 5 IF u A Q Q 0 km mm. mmJ W N a R R mm mum Eu ER. 56 m8 4 W E b5 Eu E k8 mm mm uE mm. N mm F hmMm VA ll VF y VI Q\ L T 1 m3 mm y! k3 mv AME 1 II II 1F wR \IF llkmb jRa has HS m Em? I l. N .L| NQ tmfl I. Nb F JWW 1 m H 1 my H% 5 4 iPatented Feb. 5, 1952 APPARATUS FOR PRECISION BORE GRINDING Roger S.Pyne, Longmeadow, Mass, assignor to Van Norman Company, Springfield,Mass, a corporation of Massachusetts Application August 2, 1948, SerialNo. 41,996

6 Claims.

This invention relates to a method and an apparatus for increasing theaccuracy of internal grinding, of particular utility when the bore is sosmall that there is not enough room within it for both a grinding wheeland a feeler for determining continuously the size to which the hole hasbeen ground. The method is of especial value in grinding grooves in theouter races for ball bearings, since in such cases the grinding wheelcannot be withdrawn periodically in an axial direction to permit afeeler to enter the bore, or to contact the withdrawn wheel, as issometimes done when cylindricalbores are being ground. The inventionmay, however, be applied to cylindrical bores as well as to groovegrinding and in the latter case may be used where the grinding is doneby the plunge out method as well as on an oscillating grinder. As wellas increasing the accuracy of the grinding operation the speed ofgrinding will be increased over cases where the grindin wheel has to beremoved from the work at intermediate periods in a single grinding cyclein order to gauge either the wheel or the work. Additional objects andadvantages will appear from the following description and claims.

The invention will now be described with reference to the accompanyingdrawings, in which Fig. l is a front elevation of a portion of anoscillating grinding machine designed for producing outer races for ballbearings and constructed in accordance with the present invention;

Fig. 2 is a section thereof on line 2-2 of Fig. 1;

Fig. 3 is a top plan of the rnaohine with certain parts broken away online 33 of Fig. 2;

Fig. 4 is a view of the left hand side (as "viewed in Fig. 1) of thespindle and supporting slides, with the gauging mechanism elevated intothe position assumed during the grinding cycle;

Fig. 5 is a section substantially on line 55 of -Fig. 6;

Fig. 0 is a section on line 6-6 of Fig. 3;

Figs. '7 to 14 are diagrammatic views showing successive stages in thegrinding and gauging operations; 7

Fig. 15 is a diagram of one manner of operating the mechanismautomatically; and

Fig. 16 is a continuation of Fig. 15 showing the control circuit for themain cross slide.

The grinding of a work piece in accordance with the invention may becarried on by hand control of an internal grinding machine with upperand lower cross slides to which a gauge has been added to determine theinitial position of the grinding side of the wheel relative to the maincross slide. although it is apparent that'it is preferable that thegrinding machine be controlled automatically. p

Theouter race I to be ground-is carried in a It will first be sodescribed,

I to that of a longitudinally sliding table 8.

suitable chuck 2 (Fig. 1) on an oscillating work head 3, as shown forexample in the patent to Van Norman et 211., 2,149,409, March 7, 1939;the chuck and oscillating work head being shown here in outline only.The grinding wheel 4 is mounted on a spindle 5 .arried by an upper slide5. This slide is mounted for movement transverse to the axis of thespindle on a cross slide 1, which in turn is mounted for movementparallel to that of the upper slide and transverse It will be apparentthat the wheel may be moved toward and away from the side of the borebeing ground by movement of either of the slides 6 and l, and can beinserted or withdrawn from the bore by movement of the table 8.

In accordance with the invention the motion of the slide 1 controls theonsetting and offsetting of the wheel relative to the work preparatoryto and following the grinding operation as well as the actual feeding ofthe wheel during grinding, and the slide 6 corrects the position of thewheel 4 on the slide i as the wheel wears. In addition to the otherfunctions it performs the slide 1 moves to a fixed position whichterminates the active part of the grindwork piece at the exact diameterdesired.

ing cycle. As long as the amount of stock to be removed from successivework pieces is substantially constant (it may be kept so by roughgrinding the work pieces to standard dimensions on another machine ifthe initial sizes of different pieces tend to show large dimensionaldifierences) the wear of the wheel on successive work pieces will alsobe substantially constant. Between grinding operations the slide 9 isadvanced until the active side of the grinding wheel is stopped bycontact with a feeler, to be described later, which is carried by theslide E and thus always positions the active side of the grinding wheelin a constant relation to the slide '11 at the start of a grindingoperation. During the next grinding operation the wheel will of coursewear, and by proper adjustment of the feeler the wheel can be caused toend the grinding cycle with the It is perfectly possible to grindsuccessive bores with an average variation of less than 0.0001" ,bythismethod, without making any measurement of the work piece duringgrinding. pieces should be checked periodically for size as a safetymeasure, but the tolerances mentioned can be obtained as long astemperature changes in the cooling water or ambient air, in the rate ofwear of the wheel, or other similar factors afiecting the grindingoperation incidentally, do not become too great.

As soon as the advance of the slide 1 has been stopped by reason of ithaving arrived at the fixed position referred to' above, and a suitabletime elapsed to permit the wheel to spark out if desired, the slide 6iswithdrawn a short distance Work (say a few thousandths) at a slowrate. This slow retraction, conveniently controlled by a time relay,keeps the rate at which the wheel leaves contact with the surface of thebore so low that vibration, uneven grinding, and marks on the work willbe avoided. When this distance has been traversed, the slide l and thetable 8 are moved respectively radially and axially of the work piece toremove the grinding wheel from the bore and to the gauging position atwhich it is to be set relatively to the slide I by adjustment of theupper slide 6. This adjustment sets the grinding wheel so that thenormal feeding advance of the slide 7 will just bring the work piece tothe correct diameter if the wheel wears down the expected amount. Inother words, the wheel is preset so that it would, if no work piece werepresent, stop its feeding motion at a distance beyond the correct worksurface an amount equal to the expected wear on the wheel for onegrinding cycle. It should be emphasized that it is not necessary thatthe position of the wheel at the time it is preset should be in linewith this assumedstopping position, it being sufiicient that when thewheel is preset the slide 1 is at a fixed distance from its own stoppingposition at the termination of grinding. Indeed, if the feeler by whichthe wheel is stopped in the presetting operation is, as is preferred,carried by the slide i, no definite position of that slide at the timeof presetting is required, as all that is being done is to set slide 6in a fixed position relative to slide 7.

Before continuing with a detailed discussion of the gauging operationthe structure of the machine will be considered. The main cross slide 1is provided with a lead screw 9 (Fig. l) which can be rotated by ahandwheel It or by suitable power means such as described in the VanNorman patent referred to above. As is common, the slide 1 moves in waysH on the longitudinally reciprocable table 3. The upper slide 6 moves inways E2 on the lower slide '3, and is provided with a lead screw l3 heldagainst longitudinal movement relative to the upper slide by a thrustbox [4 and threaded into a nut l5 secured firmly to the lower slide. Thelead screw i3 may be rotated by a handwheel It or by a power mechanismmounted in a housing 17. Within this housing is a motor it of a lowspeed type, preferably having about one revolution per minute. Its shaftis connected to an intermediate shaft W by gearing 20, and a worm 2i onthe shaft 19 meshes with a worm wheel 22 on the lead screw it andpreferably coupled to it through a friction clutch to permit ofoperation by the handwheel IS. The lead screw can be rotated very slowlywhen the motor is energized, so that at each cycle the slide 6 can beadvanced an amount approximately commensurate with the wear of thewheel. Since this may be on the order of a thousandth of an inch or lessthe need for very slow rotation of the lead screw is evident, as is theneed for having the parts constructed with the utmost precision andwithall possible backlash eliminated. The spindle 5 carrying the wheel 4 iscarried in a clamp bracket 23 on the slide 6, and is provided with apulley 24 by which it may be rotated by any suitable means.

The gauging mechanism by which the presetting advance of the upper slide6 is arrested is carried in a housing 25 on an arm 26 swinging upon apivot 21 on a bracket 28 secured to the lower slide 1. This slide iscarried back and forth toward and away from the work by thelongitudinally moving table, and to prevent the gauging mechanism fromstriking the work head the arm 25 has a roll 28 riding on a cam 38secured to the machine frame. As the table moves towards the work thecam lifts the arm from the position of Fig. 2 to that of Fig. 4. Whenthe table moves away from the work the arm is lowered, striking a springplunger or dashpot 3i to reduce shock and finally a positioning abutment32 which supports it in gauging position.

Withinthe gauge housing 25 is a pivot 35 on which is pivoted an arm 36having an upward extension 31 osoillatable between adjustable stops 38and 39. When the arm is in the position of Fig. 2 the extension 3'! isin contact with stop 38, and a spring contact ll! on the extension is inengagement with a screw contact 55 adjustable within the housing. Thelower end of the gauge arm 36 carries a block 42 of hard material suchas tungsten carbide which is substantially unaffected by momentarycontact withthe grinding wheel. When in its presetting position thewheel is advanced by movement of the upper slide 6 until it strikes thegauge block 42. This rocks the gauge arm 36 and breaks the contactbetween the members 40 and 4|. Preferably this activates anelectromagnet 43 which holds the arm temporarily in a position out ofcontact with the wheel.

The gauge housing 25 is adjustably mounted on the arm 26 by a clampscrew 44 extending through a slot 45 in the arm; and is provided with anadjusting screw 46 threaded into a block 4'! on the arm so that it canbe shifted parallel to the direction of movement of the slide l tochange the position of the gauge block relative thereto. The screw ispreferably provided with a graduated head 48 so that the position of thegauge block can be read directly.

The operation will now be considered with reference to Figs. 7 to 14.Fig. 7 shows the condition at the termination of the grinding operation,during which it should be remembered that there is no gauging being doneeither of the wheel or work. The grinding is stopped by the lower crossslide 1 reaching a mechanical stop or limit switch, or being manuallyarrested at a constant point as indicated by the handwheel I0. After aperiod of dwell to allow for sparking out, if desired, the upper slide 6is backed away slightly and slowly as in Fig. 8 afew thousandths of aninch to remove the wheel from contact with the work without chatter. Theoscillation and rotation of the work head then are stopped, in anyconventional or desired way, with the work piece in approximatealignment with the spindle (Fig. 9). When this has been done the slide 7is moved radially of the work (Fig. 9) and the table 8 longitudinally ofit (Fig. 10) to bring the grinding wheel to its resetting position withthe slide 1 in an accurately fixed position. As long as this position isreproduced exactly at each cycle its absolute location relative to thework piece is of no importance; and as stated above, if the gauge iscarried by the-slide i and not by a part of the machine in fixedrelation to the work piece, even this amount of absolute location is notnecessary since the wheel adjusting operation is merely one x of settingthe wheel at each cycle in a fixed posi" tion relative to the main crossslide 7. The shiftthe presetting operation is merely moving the slide 6forwardly until the wheel strikes the feeler, which is in fixed positionrelative either to the slide 1 or to the work piece. Thus the backin onoperation of Fig. 8 need not be carried on with great accuracy. I d

With the wheel thus brought to the initial pr setting position of Fig.10, a delay of two to three seconds is introduced by a time delay relayto allow vibrations to damp out. Alternatively, the backing oil byrotation of feed screw 1, described heiew in connection with Fig. 12,maybe cope at this point so as to give time for damping follo'vw ing therapid movement of Slide 1 and table s to presetting position, in whichcase no 'se1 arate delay is needed. The slide 6 is then advanced by theslow speed motor 18 untilthe wheel by strik ing the gauge block 42 andthus bre'akifig the engagement between contacts 40 and 4! stops themotor. The position in which this occurs can be regulated by theadjusting screw 46, which varies the position of the gauge block 42relative to the slide 1; and is chosen so that when the slide '5 stopsin its feeding motion at a fixed point at the end of the next grindingcycle the work piece will have been correctly ground. This is equivalentto presetting the wheel on the slide '1 so that if no work piece werepresent to cause wear, the final position of the active surface of thegrinding wheel would project beyond the axis of work rotation a distanceequal to the radius of work piece desired plus the amount of wheel wearoccurring in the grinding of a single work piece. The advance of slide 6can also be interrupted manually at a signal actuated by the gauge 42.During the gauging period the work piece is replaced with a fresh one.

With the wheel thus positioned relative to the cross slide 1 the latteris then retracted by an amount at least equal to the amount of stock tobe removed (Fig. 12) so that the wheel will clear the work piece whenintroduced within it, unless this operation has been accomplished beforethat of Fig. 11. The linkage mechanism of theVan Normanpatent (orseparate motors as will be described below) 7 is then put into operationto cause ofiset of the wheel and introduction of it Within the workpiece, and finally the feeding motion of slide 1 causes contact betweenthe wheel and work. The grinding cycle is then commenced with thesuccession of coarseand fine feeds in any manner desired, the slide 1being arrested in its motion manually, or by a stop or limit switch, ata fixed point with no necessity of gauging the work piece duringgrinding.

One manner of automatically operating the machine to produce the desiredpresetting of the grinding wheel is shown in Figs. and 16. The controlis accomplished by connecting commercial relays and switches, theconstruction of which is of no interest here, in such a manner that thesequence of operations described above will be performed automaticallyonce the machine is set in operation. The operating'coils and contactorsof each relay are, :in accordance with convention, shown separate, whichgreatly "simplifies the drawing, but the several parts or a single relayare indicated by a single -symbc l. Such symbols are keyed to themachinedescribed above in accordance with the following plan. Limitswitches are indicated by L followed by the number of the part whichoperates them, and then by F or R depending on whether they areoperated'on the forward or return-stroke, Thus LSR would be a limit switchoperating oii m'otien of table 8 away from the work. Control relays areindicated by C and time delays by T, the number following this letterindicating the part controlled. A -normally open contactor is shown byspaced lines, a normally closed one by spaced lines with a diagonalthrough them; and relay activating coils by a zig-zag line.

on depressing the starting button 43 a relay 08F in line 50 (having acontactor bridging the starting button to permit the latter to bereleased) is activated, starting the motor (not shown) which drives thetable 8 into operative position. The motor is stopped by the lirhitswitch LBF which opens the circuit through C8F. The limit switch has forthis pur ose a normauy closed contactin line 5!], but has as well anormally open contact in line 5| in series with nor-"- mally closedcontacts on a relay 01F and the activating coil of a relay G1 whichcontrols the direct current variable feed mechanism for slide '1 shownin Fig. 16. The switch LBF also controls, through a branch line 52, aseries of parallel lines 53, 5G and 55.

When C7 is activated current flows (Fig. 16) through the normally closedcontacts 58 of relay ClA through a high speed rheostat 56 through thearmature 5'5 of the motor which operates slide 1. The slide will move ata rapid traverse rate until limit switch L'iA is closed, which closesthe energizing coil of a fast-slow relay C'IA, opening contact 58 andclosing contact 59. Current then flows through the slow speed rheostatfill and through the motor armature. The relay C'IA has contacts 6|which are closed to bridge L'iA, which is closed only momentarily. Whenlimit switch L'IF is closed by slide 1 Teaching the predeterminedposition for termination of the grinding operation the relay ClF isactivated, opening the normally closedcontact in line 5| anddeactivating relay C1 to stop the feed. Contacts on relay ClF alsobridge L'IF to preserve the relay in operation. It should be stated thatthe several limit switches controlling the motion of slide 1 arepreferably mounted on the handwheel H! or a part similarly geared uprather than directly on the slide itself, in order to magnify the motionand increase the accuracy of the terminal position of the slide whengrinding ceases.

Operation of relay CIF also activates line 55 and starts the operationof a time delay relay TlF. When the contacts of this relay close, theline 82 is activated together with the relay 06R, which starts the motor[8 of slide 6 to back the wheel away from the work. The delay caused byTIF is sufiicient to permit the wheel and work to spark out, anoperation usually desired in accurate work. Closure of the T'IF contactsstarts a second time delay relay TBR. which controls the duration of therearward movement-of the upper or secondary slide. This backing away issuificient to clear the wheel gradually from the work, in order to avoidmarks; and also insures that the wheel will be positioned in gaugingposition with no possibility of striking the gauge even though the wheelmay have worn less than the estimated amount for which it was pre's'eton the preceding cycle.

When T63 has run its timing cycle its contacts in a line 63 close; andcurrent passes through a normally closed limit switch L8R and through arelay CSR which operates the motor (not shown) which drives table 8 in adirection to withdraw the wheel from the work. The relay has eoiitactorsbridging TGR so as to maintain 08R in operative position after therelease of the former. As the table 8 moves back L8F-is released,resetting relays CIA and 01F, and opening the contacts of the latterwhich are in line 55 in series with CBR. Interruption of current flowthrough the latter stops the rearward motion of slide 6.

When the table 8 reaches its out position a limit switch L8H, isactivated, having contacts in line 63 which open to interrupt thecurrent through 08R and stop the table. Contacts of LBR controlling bothlines 64 and 65 are closed to activate a time delay relay TBF which hasseveral functions. First it has normally closed contacts in line 66which when the limit switch LBR is closed activate a relay 01R whichdrives the motor of main slide '1 rearwardly, so that the wheel will bebacked off sufficiently to allow for the amount of stock to be removedfrom the next work piece. It should be noted that the absolute positionof the slide 1 during gauging is of no importance since the gauge 42moves with the slide and all that gauging does is to reposition thewheel spindle with respect to the slide.

When the time cycle of TH expires 01B is de-energized, stopping theretraction of slide 1, and contacts of TSF in line 61 are closedactivating a relay CEF which controls the motor 18 which drives thesecondary slide 8 to cause it to carry the wheel towards gauge t2. Whencontact is made the gauge opens its contact, activating an electronicrelay 68 which in turn controls a relay 69 energizing the gauge-holdingmagnet 43 and simultaneously opening the circuit in line 61 tode-energize relay 66F and arrest the forward movement of the secondaryslide. The gauging and resetting operation is now complete.

What I claim is:

1. A grinding machine comprising a main and a secondary slide eachmovable transversely to the surface of the work piece to be ground,means for moving the main slide at a feed rate to a fixed terminalposition during each grinding cycle, a grinding wheel mounted on thesecondary slide, a gauge mounted on the main slide, and means for movingthe secondary slide prior to the start of a grinding operation to bringthe active surface of the wheel into contact with the gauge- .7

2. A grinding machine comprising a main and a secondary slide eachmovable transversely to the surface of the work piece to be ground, agrinding wheel mounted on the secondary slide, means for moving the mainslide at a feed rate to a fixed terminal position during each grindingcycle and to a gauging position with the wheel removed from the workpiece between grinding cycles, a gauge mounted in fixed positionrelative to the main slide when the latter is in gauging position, andmeans for moving the secondary slide when the main slide is in gaugingposition to bring the active surface of the wheel into contact with thegauge.

3. A grinding machine comprising a main and a secondary slide eachmovable transversely to the surface of the work piece to be ground, agrinding wheel mounted on the secondary slide, a gauge mounted on themain slide, means for moving the main slide at a feed rate to a fixedterminal position during each grinding cycle and to a gauging positionwith the wheel removed from the work piece between grinding cycles, andmeans for moving the secondary slide when the main slide is in gaugingposition to bring the active surface of the wheel into contact with thegauge.

4. A grinding machine comprising a main and a secondary slide eachmovable transversely to the surface of the work piece to be ground, agrinding wheel mounted on the secondary slide, means for moving the mainslide at a feed rate to a fixed position during each grinding cycle andto a gauging position with the wheel removed from the work piece betweengrinding cycles, agauge mounted in fixed position radially of the Workpiece, means including a prime mover for moving the secondary sliderelative to the main slide, means for activating said prime mover whenthe main slide is in gauging position to move the secondary slide in adirection to cause the wheel to approach the gauge, and means forstopping the prime mover when the wheel con tacts the gauge.

5. A grinding machine comprising a main slide and a secondary slide eachmovable transversely to the surface of the work piece to be ground,

' a grinding wheel mounted on the secondary slide,

means for moving the main slide at a feed rate to a fixed positionduring each grinding cycle and to a gauging position with the wheelremoved from the work piece between grinding cycles, a gauge mounted infixed position relative to the main slide when the latter is in gaugingposition, a lead screw connecting the main and the secondary slides, aprime mover for activating said lead screw when the main slide is ingauging position for rotating the lead screw to shift the secondaryslide in a direction to move the grinding wheel toward the gauge, andmeans activated by contact between the wheel and the gauge for stoppingthe prime mover.

6. In a grinding machine comprising a slide, means for moving said slidetransversely to the surface of the work piece to be ground at a feedrate to a fixed terminal position during each grinding cycle, a grindingwheel rotatable on said slide and mounted for movement relative theretoin a direction transverse to the surface of the Work piece to be ground,a gauge fixed relative to the slide, means for moving the grinding wheelrelative to the slide prior to the start of a grinding cycle and whilethe slide is in said fixed terminal position to bring the active surfaceof the wheel into contact with the gauge, and means actuated by thegauge upon contact with the wheel for stopping further advance of thewheel relative to the slide.

' ROGER S. PYNE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,102,558 Van Norman July 7, 19141,473,520 Rosak Nov. 6, 1923 1,549,600 Mueller Aug. 11, 1925 1,602,680Knowles Oct. 12, 1926 1,840,231 Harrison et al. Jan. 5, 1932 1,872,667Bryant Aug. 23, 1932 1,914,995 Guild June 20, 1933 1,997,978 Raule Apr.16, 1935 2,050,261 Blood Aug. 11, 1936 2,092,876 Cramer Sept. 14, 19372,127,210 Dunbar Aug. 16, 1938 2,141,853 Brown Dec. 27, 1938 2,280,692Elberty Apr. 21, 1942 2,326,339 Dudgeon Aug. 10,1943

